Elaborate drawings are great but not everyone has the time or skills to create one. Often, a quick sketch can get the message across just as well. Especially if you're brainstorming and looking for as many ideas as possible. When you choose an idea to flesh out, the sketch can then be fleshed out, too, if you want.
The sketch above was one of several done to convey a coaching session, done with a Sharpie marker. Sketching with a bold marker makes it much easier to share online. And if you you want to use that sketch at some point, you're ready to go - no redrawing necessary.